We literally have no idea how many houses could be in there. Image: Getty.

We may be getting better at building more houses but unfortunately we’re not very good at counting them.

In August, the housing minister was citing the latest DCLG New Build statistics as proof that the country is building again. Completions across England had apparently reached 153,000 in the year to June 2017, “the highest level since 2008”. On this basis, the minister may be pleasantly surprised and slightly confused when he reads the DCLG’s Net Supply release in November and finds out that housebuilding completions had already reached 155,000 in 2014-15, and are actually much higher.

The housing minister can perhaps be forgiven some excitement over the first release of housebuilding statistics during his tenure. Based on the average tenure of previous housing ministers, he’s probably only got another three or four to look forward to. However, despite some allowance for over-excitement, it is irresponsible for the housing minister to be quoting the New Build statistics as absolute measures of housebuilding as they under-count the number of new homes actually being built.

It is particularly irresponsible because DCLG are well aware that there are issues with the New Build statistics. In the introduction to their New Build statistical release they suggest the New Build figures should only be “regarded as a leading indicator of overall housing supply”, and instead the Net Supply release “is the primary and most comprehensive measure of housing supply”.

The scale of the under-count is apparent when comparing the New Build data to the more comprehensive Net Supply release. While the Net Supply release includes conversions, changes of use, and demolitions to calculate the net change in dwellings, it also includes a more comprehensive measure of housebuilding.

The latest available Net Supply data for 2015-16 recorded 164,000 housebuilding completions across England compared to only 140,000 completions recorded in the New Build data. That suggests the New Build release is currently missing around 15 per cent of the housebuilding market.

Beyond the widespread confusion created by the publication of different housebuilding numbers, this issue has important consequences for policy makers. Our failure to accurately measure housebuilding and our limited understanding of who is doing the building make it very difficult to accurately assess the success or failure of existing policies and identify new ones that could increase new supply.

The exact reasons for the under-count are not confirmed but it appears to be linked to the falling market share of the largest provider of warranties on new homes. The National Home Building Council (NHBC) provides a substantial share of the data used to create the New Build statistics, and it’s been widely assumed that they have a market share of around 80 per cent. Based on an assumed market share, the NHBC data is grossed up to provide a measure for the whole market alongside other sources of building control inspection data.

However, recent years have seen a broader range of groups delivering new homes. Volume housebuilders still deliver the majority of new homes but there has been an increase in activity by SME housebuilders, high-density luxury developers, build-to-rent investors, and housing associations. For some of the firms and organisations in these groups, an NHBC warranty may be too expensive or not attractive compared to the alternatives. NHBC’s market share has probably fallen over this period.

A fall in NHBC’s market share is apparently confirmed by the request for a review of its market undertakings from the Competition & Markets Authority (CMA). Although most of the market share data published by the NHBC and the CMA in the review is confidential, there is an interesting finding in the CMA’s provisional decision (paragraph 4.32). Using new home data from nine warranty providers including NHBC, the CMA estimated the NHBC market share at around 70 per cent.

If, instead of grossing up the NHBC data by 80 per cent market share, we use 70 per cent then we would expect the DCLG New Supply data to be around 14 per cent higher (0.8/0.7). That difference would account for nearly all of the shortfall in the New Build completions when compared to the Net Supply housebuilding data. While there may be other factors causing the under-count, it would appear that this market share issue is the most significant factor.

It would be great if we had an accurate and regularly updated measure of housebuilding, but it turns out that counting houses is actually quite difficult. The Net Supply data is far from perfect, and it’s only released once a year with a substantial delay but it’s the best we currently have.

Meanwhile, in Ireland they’ve had the opposite problem, with an over-count of new homes. Official completions data uses electricity connections – but it turned out that the actual number of new build completions between 2011 and 2015 was 42 per cent lower than the official figures due to a large number of re-connections.

Until we see a substantial re-working of the DCLG’s New Build statistics, it appears the best option is to assess the full range of available indicators that cover both housebuilding and total supply. However, perhaps the biggest frustration is that DCLG are aware of the issues with the New Build statistics yet we still see quarterly political point scoring based on these flawed data. Given the complexities of the housing market, it is only once we move past this short-term politicking that we have any hope of solving the crisis.

Neal Hudson is an independent housing analyst, who tweets as @resi_analyst. This article originally appeared on his blog.

A couple of weeks ago, someone on Twitter asked CityMetric’s editor about the longest possible UK train journey where the stations are all in progressive alphabetical order. Various people made suggestions, but I was intrigued as to what that definitive answer was. Helpfully, National Rail provides a 3,717 page document containing every single timetable in the country, so I got reading!

(Well, actually I let my computer read the raw data in a file provided by ATOC, the Association of Train Operating Companies. Apparently this ‘requires a good level of computer skills’, so I guess I can put that on my CV now.)

Here’s what I learned:

1) The record for stops in progressive alphabetical order within a single journey is: 10

The winner is the weekday 7.42am Arriva Trains Wales service from Bridgend to Aberdare, which stops at the following stations in sequence:

The second longest sequence possible – 8 – overlaps with this. It’s the 22:46pm from Cardiff Central to Treherbert, although at present it’s only scheduled to run from 9-12 April, so you’d better book now to avoid the rush.

Not quite sure what you’ll actually be able to do when you get to Trehafod at half eleven. Maybe the Welsh Mining Experience at Rhondda Heritage Park could arrange a special late night event to celebrate.

There is a chance for a bit of CONTROVERSY with the last one, as you could argue that the final station is actually called London St Pancras. But St Pancras International the ATOC data calls it, so if you disagree you should ring them up and shout very loudly about it, I bet they love it when stuff like that happens.

Alphabetical train journeys not exciting enough for you?

2) The longest sequence of stations with alliterative names: 5

There are two ways to do this:

Ladywell, Lewisham, London Bridge, London Waterloo (East), London Charing Cross – a sequence which is the end/beginning of a couple of routes in South East London.

4) The greatest number of stations you can stop at without changing trains: 50

On a veeeeery slow service that calls at every stop between Crewe and Cardiff Central over the course of 6hr20. Faster, albeit less comprehensive, trains are available.

But if you’re looking for a really long journey, that’s got nothing on:

5) The longest journey you can take on a single National Rail service: 13 hours and 58 minutes.

A sleeper service that leaves Inverness at 7.17pm, and arrives at London Euston at 9.15am the next morning. Curiously, the ATOC data appears to claim that it stops at Wembley European Freight Operations Centre, though sadly the National Rail website makes no mention of this once in a lifetime opportunity.

6) The shortest journey you can take on a National Rail service without getting off en route: 2 minutes.

Starting at Wrexham Central, and taking you all the way to Wrexham General, this service is in place for a few days in the last week of March.

7) The shortest complete journey as the crow flies: 0 miles

Because the origin station is the same as the terminating station, i.e. the journey is on a loop.

8) The longest unbroken journey as the crow flies: 505 miles

Taking you all the way from Aberdeen to Penzance – although opportunities to make it have become rarer. The only direct service in the current timetable departs at 8.20am on Saturday 24 March. It stops at 46 stations and takes 13 hours 20 minutes. Thankfully, a trolley service is available.

9) The shortest station names on the network have just 3 letters

Ash, Ayr, Ely, Lee, Lye, Ore, Par, Rye, Wem, and Wye.

There’s also I.B.M., serving an industrial site formerly owned by the tech firm, but the ATOC data includes those full stops so it's not quite as short. Compute that, Deep Blue, you chess twat.

10) The longest station name has 33 letters excluding spaces

Okay, I cheated on this and Googled it – the ATOC data only has space for 26 characters. But for completeness’ sake: it’s Rhoose Cardiff International Airport, with 33 letters.

No, I’m not counting that other, more infamous Welsh one, because it’s listed in the database as Llanfairpwll, which is what it is actually called.

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